(1) Field of the Invention
The present invention relates to a broadcast receiving apparatus for receiving a broadcast, and particularly to a system for executing a program that refers to a scrambled broadcast signal, in the broadcast receiving apparatus.
(2) Description of the Prior Art
Broadcast signals are sent from a broadcast station and include a wide variety of information. Among such information, there are those within which access authorization is set for each user. For example, video and audio information that can be viewed only by users who have signed contracts are transmitted in sports channels and movie channels.
The Conditional Access System (CAS) is introduced as a system for implementing such a format. A broadcast station performs scrambling on information that is accessible only to identified users, and such data is transmitted by being included in a broadcast signal. At the same time, a key necessary for descrambling, additional information such as contract information to be transmitted to specific users, and so on, are transmitted by the broadcast station together with the scrambled information.
When a user accesses scrambled information, the broadcast receiving apparatus judges whether the user holds an authorization for accessing such information. If access is possible, it performs descrambling using a device found in the broadcast receiving apparatus known as a descrambler, after which, it accesses the descrambled information.
In an environment such as this, there is a need for the broadcast receiving apparatus to judge the access authorization of a user. However, in addition, there is a need to judge “which information” is to be descrambled “at which timing”.
In official publication of Japanese Laid-Open Patent Application No. 4-32392, a detailed description is made regarding a technique where a broadcast receiving apparatus retains a scrambled channel beforehand, and if the scrambled channel is selected during the channel selection by a user, it is automatically passed through an external descrambler connected outside the broadcast receiving apparatus. In this patent, descrambling is carried out on “the selected channel”, “at the time of selection”.
In addition, at present, specifications regarding environments for the execution of a program on a broadcast receiving apparatus are being developed and operated in many areas. For example, a specification known as Digital Video Broadcasting-Multimedia Home Platform (DVB-MHP) has been laid out in Europe, and operation conforming to such specifications is already being initiated. Furthermore, a specification associated with the cable broadcasting environment, known as Open Cable Application Platform (OCAP), is being laid out in the United States, with operations scheduled to start in 2005. In an environment such as this, a program executed on a broadcast receiving apparatus can freely access information within a broadcast signal, using devices existing in the broadcast receiving apparatus. For example, an MPEG-2 transport stream received by the broadcast receiving apparatus can be changed using a tuner device. For example, using an AV decoder device, video/audio information transmitted by an MPEG-2 transport stream received by the broadcast receiving apparatus can be decoded and outputted on a display/speaker. For example, data for data broadcasting, program information, or the like, transmitted by an MPEG-2 transport stream received by the broadcast receiving apparatus can be obtained using a section filter.
In an environment such as this, there instances in which the information which the program tries to access is scrambled and transmitted. In such a case, the devices in the broadcast receiving apparatus cannot use the information, scrambled as it is. As such, there is a need to descramble the scrambled information.
As one technique, there is a method where the broadcast receiving apparatus provides a program operating on the broadcast receiving apparatus with a library for the purpose of descrambling. Before accessing the scrambled information, the program starts descrambling by using the descrambling library. In this method, the program itself judges the timing of the descrambling.
However, this method requires the program itself to make considerations regarding the scrambling of the information to be accessed. Descrambling with regard to a channel with which a contract is previously entered into, is not the only pattern in descrambling. There is also a pattern where programs are purchased on the spot such as Pay-Per-View (PPV), where billing is done on a per program basis, so there are cases which require complex processing. As a result, there is the disadvantage of making the implementation of the program itself more complex.